Casino managers have always been interested in being able to record in real time all the bets occurring within their premises. To do so a precise and reliable means of identifying the various chips (gaming tokens) placed inside and outside the betting zones, as indicated by gaming surface (gaming table) markings, is required.
Such capability has, up to now, been impossible to achieve, within reasonable budgets and with existing technologies, but it nevertheless still remains extremely high in the list of the casino managers' priorities. For example, such capability, combined with appropriate software, could allow the real-time automatic flagging of unusual events, the continuous tracking of the performance of individual players, as well as the assessment of the short, medium and long-term performance of casino personnel.
During the past years, several approaches have been proposed to achieve this objective. In particular, approaches specifically based on radio frequency identification (RFID) technology have been patented. However, although promising, this technology presents a major drawback: it is not particularly precise in terms of spatial resolution and, as a result, its potential is limited to gaming surfaces with single betting areas, such as poker tables, or to tables with very spaced out betting areas.
In fact, a commonly used type of RFID technology is based on radiated fields (far fields) operating at approved frequencies such as 433 MHz, 915 MHz, 2.4 GHz etc. Because of both its operating principle and the frequencies at which it operates, this technology is subject to effects that disturb the local field. For example antennas may be detuned by parasitic capacitance (people and metal objects), signals may be attenuated by the human body, and propagation may be affected by multi-path phenomena. Consequently, it is easy to see why, when dealing with gaming surfaces with multiple, closely spaced, betting areas, such as the ones used in blackjack or baccarat, or, even worse, with gaming surfaces in which chips may legitimately ride on the separation lines between betting areas, such as roulette tables, existing RFID based technology is inadequate.
Magnetic coupling RFID based technology, operating at approved frequencies in the 125 KHz or 13.56 MHz bands, has been proposed to overcome these spatial resolution limitations. Because of the inherent “near field” characteristics of this technology, the signal dies off very rapidly beyond the intended coverage area and surrounding environment variations have much less of an impact.
However, even though this technology is clearly superior to other existing RFID technology, it may not be, by itself, used to achieve accurate enough coverage over closely spaced betting zones. In fact, this is due to another requirement imposed by casinos: as chips may be stacked on top of each other, the technology has to allow communication with a chip on top of a stack, which may actually be up to 25 chips high. The magnetic field produced by an embedded loop is roughly spherically shaped and its “drop off” characteristics are determined by physics and may be expressed in dB/mm. To extend itself high enough to read the chips at the top of a stack, the magnetic field inevitably has to extend laterally as well. This implies that when the diagonal of the betting area is smaller than the height of the top of a 25 chip stack, and that an adjacent betting area is situated quite close to the observed betting area, it is generally impossible to achieve the required “drop off” characteristics.